Fungicides are common ingredients in paint formulations where they are used to provide protection against mold and mildew growth in latex paint formulations and against attack by such organisms feeding on paint film polymers. Typically the effects of such fungicides in paint films are limited to the immediate surface of the film.
In U.S. Pat. No. 3,549,762 there is described an alkyd paint formulation which employs 2,4-dicyanotrichloropyridine as a biocide and which exhibits a zone of inhibition beyond the surface of the paint film in which a fungal species would not grow.
Air handling equipment is used in all types of buildings for heating, ventilating and air conditioning. This air handling equipment circulates air throughout the whole building on a continual basis. As air moves through the system, it carries with it suspended matter that gets deposited in the duct work, and builds up over time. This build-up can be dust, dirt, or grease and volatile food components from food preparation areas. Greasy substances are a particular problem, as they tend to adhere to the interior surface of the air handling equipment. Under the right conditions, this build-up can be the breeding ground for various fungus or bacteria, giving rise for some odor problems and possible serious health problems. A particularly serious problem exists when mold, bacteria or fungus is present in an isolated part of the building, and because of the air circulation system, it is distributed throughout the whole building. This is a special concern in hospitals and health care centers, as well as buildings with commercial kitchens. There are reported known instances where disease has been spread to occupants in a building through the air handling equipment.
Air handling equipment requires periodic cleaning operations in order to clean the interior surfaces as well as sanitize them with special sanitizing solutions. In some cases the equipment is actually broken into and cleaned by hand or by self-propelled moving carts that scrub the surfaces as they move through the duct work. Sanitizing solution may be fogged into one of the air inlets, with fogging continuing until a cheese cloth draped over all of the ventilators becomes wet with the fogging solution, indicating the solution has moved throughout the entire duct work. This method does not remove any matter, but only attempts to kill off any fungal or bacterial growth.
Treatment of heating, ventilation and air conditioning (HVAC) systems to control mold spores is the subject of U.S. Pat. No. 3,591,328. The procedure of this reference involves injecting an aerosol of a fungicide and a film-former in a solvent solution into the air handling system using the system's air stream to disperse the aerosol throughout the system and then dry the solvent. There is no way to be assured that 100% coverage has been obtained, and it is unlikely that a complete film would be obtained throughout the air handling system. There is also a problem of hazards associated in using a solvent-borne product in an air handling system. The building would have to be evacuated and all of the air would have to be ventilated outside for several days in order to remove all solvent vapors before the building could be reoccupied. The treatment is reported to be effective for up to ninety days after which it must be presumably repeated.
Recently it has been suggested that use of a paint containing an antimicrobial agent (INTERCEPT.RTM.) in HVAC systems can be beneficial in reducing accumulation of mold and mildew when used in conjunction with preventative cleanings. However, this suggestion has not produced a product providing a practical long-life solution to the problem of fungal growth in HVAC systems.